> Because the
chief aim of sacred doctrine is to teach the knowledge of God,
not only as He is in Himself, but also as He is the beginning of
things and their last end, and especially of rational creatures,
as is clear from what has been already said, therefore, in our
endeavor to expound this science, we shall treat: (1) Of God; (2)
Of the rational creature's advance towards God; (3) Of Christ,
Who as man, is our way to God.
> In treating of God
there will be a threefold division, for we shall consider: (1)
Whatever concerns the Divine Essence; (2) Whatever concerns the
distinctions of Persons; (3) Whatever concerns the procession of
creatures from Him.
> Concerning the Divine Essence,
we must consider: (1) Whether God exists? (2) The manner of His existence,
or, rather, what is NOT the manner of His existence; (3) Whatever
concerns His operations---namely, His knowledge, will, power.
> Concerning the first, there are three points of inquiry:
> (1) Whether the proposition "God exists" is self-evident?
> (2) Whether it is demonstrable?
> (3) Whether God exists?
Objection 1: It seems that the existence of God is
self-evident. Now those things are said to be self-evident to us
the knowledge of which is naturally implanted in us, as we can
see in regard to first principles. But as Damascene says (De Fide
Orth. i, 1,3), "the knowledge of God is naturally implanted in all."
Therefore the existence of God is self-evident.
> Objection 2: Further, those things are said to be self-evident which are known as soon as the terms are known, which the Philosopher (1 Poster. iii) says is true of the first principles of demonstration. Thus, when the nature of a whole and of a part is known, it is at once recognized that every whole is greater than its part. But as soon as the signification of the word "God" is understood, it is at once seen that God exists. For by this word is signified that thing than which nothing greater can be conceived. But that which exists actually and mentally is greater than that which exists only mentally. Therefore, since as soon as the word "God" is understood it exists mentally, it also follows that it exists actually. Therefore the proposition "God exists" is self-evident.
3: Further, the existence of truth is self-evident. For
whoever denies the existence of truth grants that truth does not
exist: and, if truth does not exist, then the proposition "Truth
does not exist" is true: and if there is anything true, there must
be truth. But God is truth itself: "I am the way, the truth, and
the life" (Jn.
14:6) Therefore "God exists" is self-evident.
the contrary, No one can mentally admit the opposite of
what is self-evident; as the Philosopher (Metaph. iv, lect. vi)
states concerning the first principles of demonstration. But the
opposite of the proposition "God is" can be mentally admitted:
"The fool said in his heart, There is no God" (Ps.
52:1). Therefore, that God exists is not self-evident.
I answer that, A thing can be self-evident in either
of two ways: on the one hand, self-evident in itself, though not
to us; on the other, self-evident in itself, and to us. A proposition
is self-evident because the predicate is included in the essence
of the subject, as "Man is an animal," for animal is contained
in the essence of man. If, therefore the essence of the predicate
and subject be known to all, the proposition will be self-evident
to all; as is clear with regard to the first principles of demonstration, the
terms of which are common things that no one is ignorant of, such
as being and non-being, whole and part, and such like. If, however,
there are some to whom the essence of the predicate and subject is
unknown, the proposition will be self-evident in itself, but not
to those who do not know the meaning of the predicate and subject
of the proposition. Therefore, it happens, as Boethius says (Hebdom.,
the title of which is: "Whether all that is, is good"), "that there
are some mental concepts self-evident only to the learned, as that
incorporeal substances are not in space." Therefore I say that
this proposition, "God exists," of itself is self-evident, for
the predicate is the same as the subject, because God is His own
existence as will be hereafter shown (Question
, Article ). Now
because we do not know the essence of God, the proposition is not
self-evident to us; but needs to be demonstrated by things that
are more known to us, though less known in their nature---namely,
> Reply to Objection 1: To
know that God exists in a general and confused way is implanted
in us by nature, inasmuch as God is man's beatitude. For man naturally
desires happiness, and what is naturally desired by man must be
naturally known to him. This, however, is not to know absolutely
that God exists; just as to know that someone is approaching is
not the same as to know that Peter is approaching, even though
it is Peter who is approaching; for many there are who imagine
that man's perfect good which is happiness, consists in riches,
and others in pleasures, and others in something else.
Reply to Objection 2: Perhaps not everyone who hears
this word "God" understands it to signify something than which
nothing greater can be thought, seeing that some have believed
God to be a body. Yet, granted that everyone understands that
by this word "God" is signified something than which nothing greater
can be thought, nevertheless, it does not therefore follow that
he understands that what the word signifies exists actually, but
only that it exists mentally. Nor can it be argued that it actually
exists, unless it be admitted that there actually exists something
than which nothing greater can be thought; and this precisely is
not admitted by those who hold that God does not exist.
Reply to Objection 3: The existence of truth in general
is self-evident but the existence of a Primal Truth is not self-evident
Objection 1: It seems that the existence of God cannot
be demonstrated. For it is an article of faith that God exists.
But what is of faith cannot be demonstrated, because a demonstration
produces scientific knowledge; whereas faith is of the unseen (Heb.
11:1). Therefore it cannot be demonstrated that God exists.
Objection 2: Further, the essence is the middle term
of demonstration. But we cannot know in what God's essence consists,
but solely in what it does not consist; as Damascene says (De Fide
Orth. i, 4). Therefore we cannot demonstrate that God exists.
Objection 3: Further, if the existence of God were
demonstrated, this could only be from His effects. But His effects
are not proportionate to Him, since He is infinite and His effects
are finite; and between the finite and infinite there is no proportion.
Therefore, since a cause cannot be demonstrated by an effect not
proportionate to it, it seems that the existence of God cannot
> On the contrary, The
Apostle says: "The invisible things of Him are clearly seen, being
understood by the things that are made" (Rm.
1:20). But this would not be unless the existence of God could
be demonstrated through the things that are made; for the first
thing we must know of anything is whether it exists.
I answer that, Demonstration can be made in two ways:
One is through the cause, and is called "a priori," and this is
to argue from what is prior absolutely. The other is through the
effect, and is called a demonstration "a posteriori"; this is to
argue from what is prior relatively only to us. When an effect is
better known to us than its cause, from the effect we proceed to
the knowledge of the cause. And from every effect the existence
of its proper cause can be demonstrated, so long as its effects
are better known to us; because since every effect depends upon
its cause, if the effect exists, the cause must pre-exist. Hence
the existence of God, in so far as it is not self-evident to us,
can be demonstrated from those of His effects which are known to
> Reply to Objection 1: The existence
of God and other like truths about God, which can be known by
natural reason, are not articles of faith, but are preambles to
the articles; for faith presupposes natural knowledge, even as
grace presupposes nature, and perfection supposes something that
can be perfected. Nevertheless, there is nothing to prevent a man,
who cannot grasp a proof, accepting, as a matter of faith, something
which in itself is capable of being scientifically known and demonstrated.
Reply to Objection 2: When the existence of a cause
is demonstrated from an effect, this effect takes the place of
the definition of the cause in proof of the cause's existence.
This is especially the case in regard to God, because, in order
to prove the existence of anything, it is necessary to accept as
a middle term the meaning of the word, and not its essence, for
the question of its essence follows on the question of its existence.
Now the names given to God are derived from His effects; consequently,
in demonstrating the existence of God from His effects, we may
take for the middle term the meaning of the word "God".
Reply to Objection 3: From effects not proportionate
to the cause no perfect knowledge of that cause can be obtained.
Yet from every effect the existence of the cause can be clearly
demonstrated, and so we can demonstrate the existence of God from
His effects; though from them we cannot perfectly know God as He
is in His essence.
1: It seems that God does not exist; because if one of two
contraries be infinite, the other would be altogether destroyed.
But the word "God" means that He is infinite goodness. If, therefore, God
existed, there would be no evil discoverable; but there is evil
in the world. Therefore God does not exist.
2: Further, it is superfluous to suppose that what can be
accounted for by a few principles has been produced by many. But
it seems that everything we see in the world can be accounted for by
other principles, supposing God did not exist. For all natural
things can be reduced to one principle which is nature; and all
voluntary things can be reduced to one principle which is human
reason, or will. Therefore there is no need to suppose God's existence.
> On the contrary, It is said in the person of God: "I am Who am." (Ex. 3:14)
> I answer that, The existence of God can be proved in five ways.
> The first and more manifest
way is the argument from motion. It is certain, and evident to
our senses, that in the world some things are in motion. Now whatever
is in motion is put in motion by another, for nothing can be in
motion except it is in potentiality to that towards which it is
in motion; whereas a thing moves inasmuch as it is in act. For
motion is nothing else than the reduction of something from potentiality
to actuality. But nothing can be reduced from potentiality to actuality,
except by something in a state of actuality. Thus that which is
actually hot, as fire, makes wood, which is potentially hot, to
be actually hot, and thereby moves and changes it. Now it is not
possible that the same thing should be at once in actuality and
potentiality in the same respect, but only in different respects.
For what is actually hot cannot simultaneously be potentially hot;
but it is simultaneously potentially cold. It is therefore impossible
that in the same respect and in the same way a thing should be
both mover and moved, i.e. that it should move itself. Therefore,
whatever is in motion must be put in motion by another. If that
by which it is put in motion be itself put in motion, then this
also must needs be put in motion by another, and that by another
again. But this cannot go on to infinity, because then there would
be no first mover, and, consequently, no other mover; seeing that
subsequent movers move only inasmuch as they are put in motion
by the first mover; as the staff moves only because it is put in
motion by the hand. Therefore it is necessary to arrive at a first
mover, put in motion by no other; and this everyone understands
to be God.
> The second way is from the nature of the
efficient cause. In the world of sense we find there is an order
of efficient causes. There is no case known (neither is it, indeed,
possible) in which a thing is found to be the efficient cause of
itself; for so it would be prior to itself, which is impossible.
Now in efficient causes it is not possible to go on to infinity,
because in all efficient causes following in order, the first is
the cause of the intermediate cause, and the intermediate is the
cause of the ultimate cause, whether the intermediate cause be
several, or only one. Now to take away the cause is to take away the
effect. Therefore, if there be no first cause among efficient causes,
there will be no ultimate, nor any intermediate cause. But if in
efficient causes it is possible to go on to infinity, there will
be no first efficient cause, neither will there be an ultimate
effect, nor any intermediate efficient causes; all of which is
plainly false. Therefore it is necessary to admit a first efficient
cause, to which everyone gives the name of God.
third way is taken from possibility and necessity, and runs thus.
We find in nature things that are possible to be and not to be,
since they are found to be generated, and to corrupt, and consequently,
they are possible to be and not to be. But it is impossible for
these always to exist, for that which is possible not to be at
some time is not. Therefore, if everything is possible not to be,
then at one time there could have been nothing in existence. Now
if this were true, even now there would be nothing in existence,
because that which does not exist only begins to exist by something
already existing. Therefore, if at one time nothing was in existence,
it would have been impossible for anything to have begun to exist;
and thus even now nothing would be in existence---which is absurd.
Therefore, not all beings are merely possible, but there must exist
something the existence of which is necessary. But every necessary
thing either has its necessity caused by another, or not. Now it
is impossible to go on to infinity in necessary things which have
their necessity caused by another, as has been already proved in
regard to efficient causes. Therefore we cannot but postulate the
existence of some being having of itself its own necessity, and
not receiving it from another, but rather causing in others their
necessity. This all men speak of as God.
> The fourth
way is taken from the gradation to be found in things. Among beings
there are some more and some less good, true, noble and the like.
But "more" and "less" are predicated of different things, according
as they resemble in their different ways something which is the
maximum, as a thing is said to be hotter according as it more nearly
resembles that which is hottest; so that there is something which
is truest, something best, something noblest and, consequently,
something which is uttermost being; for those things that are greatest
in truth are greatest in being, as it is written in Metaph. ii.
Now the maximum in any genus is the cause of all in that genus;
as fire, which is the maximum heat, is the cause of all hot things.
Therefore there must also be something which is to all beings the
cause of their being, goodness, and every other perfection; and
this we call God.
> The fifth way is taken from the
governance of the world. We see that things which lack intelligence, such
as natural bodies, act for an end, and this is evident from their
acting always, or nearly always, in the same way, so as to obtain
the best result. Hence it is plain that not fortuitously, but designedly, do
they achieve their end. Now whatever lacks intelligence cannot
move towards an end, unless it be directed by some being endowed
with knowledge and intelligence; as the arrow is shot to its mark by
the archer. Therefore some intelligent being exists by whom all
natural things are directed to their end; and this being we call
> Reply to Objection 1: As Augustine
says (Enchiridion xi): "Since God is the highest good, He would not
allow any evil to exist in His works, unless His omnipotence and
goodness were such as to bring good even out of evil." This is
part of the infinite goodness of God, that He should allow evil
to exist, and out of it produce good.
> Reply to
Objection 2: Since nature works for a determinate end under
the direction of a higher agent, whatever is done by nature must
needs be traced back to God, as to its first cause. So also whatever
is done voluntarily must also be traced back to some higher cause
other than human reason or will, since these can change or fail;
for all things that are changeable and capable of defect must be traced
back to an immovable and self-necessary first principle, as was
shown in the body of the Article.